Ok, then you will have to backup a different way. Have you done it before?
There are different ways to do it.
But can you boot up the Zorin iso and provide us a print screen of the drive which is present in the computer right now.
You can do this with the Gparted app.
Okay.
Screenshot of GParted
Hello sir, I am sorry to forget that I have used only 148 GB on this pc. By mistakenly I have told you about the harddisk in my another PC 
No worries there my good friend. You're doing perfect.
Just as I thought you have enough space to use as a backup.
You can use gparted to create a separate partition of 200GB.
After this you can startup the file manager, so you can manage your backup data. Copy the files you want to keep to the newly created partition.
When done you can start the installation and make sure you install the system to the first partition which already has Zorin.
You will have to format this and install the system once again.
Hope I am clear enough?
Here in this trial mode, the date is correct but the time is not correct. It's now 10: 16 am but it is showing the time as 4:45 pm
Okay, sir, I have created the partition but can I backup my apps and restore them after the full installation with this process??
I'm afraid not. Most of the apps are installed with the system and have dependencies. So when you back them up they won't work properly.
Are there apps which you want to keep because most of them can be installed from the Software store or by using synaptic.
I have a lot of outside applications installed in my previous os. And I have downloaded most of them from the internet. Some apps are very hard to install. I have a limited one-day data pack to 2 GB so again installing those apps will take around the time of a whole month or more than that. Installing all that apps again will be a very big pain for me.
Is there any way to backup apps?
(I think you can understand my problem.)
Can I ask if the limited data pack of 2GB isn't the cause of the wifi problem?
Second, are these Linux apps? And I do understand your problem.
But still you will have to make a decision, whether you want to try recover the previous installed OS, which will be rather complicated, seeing the previous attempts you made with the other volunteers or reinstall the OS but have a loss of the already installed apps.
Yes, reinstalling will be difficult for you, expecially with the limited data pack.
Sorry sir, I don't get your question.
The limited data pack of 2GB is from your internet provider, right?
So this morning you started a new data pack of 2 GB?
(perhaps that's not the problem, just a thought)
Still you will have to make a decision whether to proceed and tackle the wifi problem on the existing OS or backup your data, loose the apps an reinstall the system. But backing up your data is always ok but you will have to decide what to keep.
I'm afraid I will have to cut loose because it been a late night for me its past 6:30 am here and I have to catch some sleep.
You think it over, what to backup and hopefully the other volunteers will try to help you further.
Okay, Thank you very much, sir. Have a sweet dream
Yes sir
I took a look at Unity (engine) and Unity hub (appimage). Sadly, the instillation is a bit complex and not easily moved. Reinstallation of Unity is the only way.
Sir, Can I once see my previous software list again so that I can note it and easily install them after the installation of Zorin os?
Is there any process for again seeing my previous software's list?
Yes, it is possible. If you boot from LiveUSB, you must first mount the partition you want to recover your installed list from.
Change XY to the Actual Drive Letters of the drive you need to mount
sudo mount /dev/sdaXY /mnt
navigate to that mount point with your terminal cd command and run:
find /var/lib/dpkg/info/ -name "*.list" -type f -printf "%P\n" | awk -F'.' '{print $1}'
You can also add to that command above to save the output as a text file (Change /path/to... to the Actual Path Location you want to use):
> /path/to/save/location/installed-old-list.txt
So it would look like:
find /var/lib/dpkg/info/ -name "*.list" -type f -printf "%P\n" | awk -F'.' '{print $1}' > /path/to/save/location/installed-old-list.txt
Sir, how to copy files from one partition to another.
That depends on how you are accessing them. If using the file manager as described above: Drag and drop.