Well, I got new task this week to upgrade older site from 3.x to 5.x. So I have no idea about this. Then i started my research mu come across with some docs which i am going to past below.
Migrating to v4: https://getbootstrap.com/docs/4.0/migration/
Migrating to v5: https://getbootstrap.com/docs/5.0/migration/
- In the newer version, there is no need for jQuery.
- Code diff: https://www.diffchecker.com/Zk1CuagM/