Hi again!
Reading this: https://docs.moodle.org/38/en/Assignment_upgrade_tool
"Assignment upgrade tool was removed from core Moodle in 3.6."
We have 3.6.1 now
I could locate assignment upgrade lib in GitHub (https://github.com/moodle/moodle/blob/master/mod/assign/upgradelib.php). Could someone help me to how to execute it to upgrade our old assignments?