How to upgrade r-base on Zorin OS Core 15.3?

Hello, I would like to know how to upgrade r-base 3.4 to r-base 3.6 or 4.0

Thanks

In the 18.04 Main Repo, 3.4.4 is the highest version.

You may try the focal 3.6 in a .deb here:
http://ports.ubuntu.com/pool/universe/r/r-base/r-base_3.6.3-2_all.deb