Sorry, there's no support for skipping over major versions, your client evaded nearly 20 years of upgrades, so getting to the point where you can use WorkBench 8.0 will be painful.
For an active MySQL 3.x installation, the only approach really is to create a full mysqldump of existing data, then
on a test machine, for each of mysql 5.0, 5.1, 5.5, 5.6, 5.7 and finally 8.0 ...
1 download & install that MySQL version
2 review that version's release notes, or for versions >= 5.0 review entries in
https://www.artfulsoftware.com/infotree/mysql_incompat.html for that version, look for issues which are likely to impact the client's DB and app
3 import the mysqldump
4 test all relevant functionalities, update my.cnf/ini as needed, fix all errors and regressions that you find
5 create a full mysqldump
6 resume at #1 with the next version
... up to and including 8.0.
Once that's sorted, you can delete the existing 3.x MySQL installation and its databases from the production machine, install 8.0, bring in the updated my.cnf/ini, import the mysqldump script from the 8.0 instance you populated and tested, test once again.
Edited 1 time(s). Last edit at 08/14/2021 12:09PM by Peter Brawley.