Is it posibble to upgrades from 3.6 to 4.xx？

How hard is it?  If it's too hard, my boss may decide changing the platform.

It depends on customization that you have in 3.60. But in most cases it's quite simple. Please find more about upgrading at https://docs.nopcommerce.com/en/installation-and-upgrading/upgrading-nopcommerce.html

quick question. i need to upgrade nop from 3.9 to 4.4
is it easyer to just installa new nop 4.4 version and then import the data from each table to the new one? or should i do the normal upgrade throught each version?

There will be a lot of differnces in the database so provided you dont have a customised database then just run the scripts 3.9->4.0, 4.0-> 4.1, 4.1-> 4.2, 4.2->4.3
Then you just use the 4.40 website on you system
And follow the instructions to upgrade 4.3 to 4.4 which does not use a script

ok thank you, i'll try that way