I have been away from development for a while, hence, my questions:
Time is a relative concept, but from API version 21 security has been tightened so that you have to add and/or permissions in the manifest file or you no longer have access to a certain directory location. This can therefore have quite a big impact on your "old" program. In addition to the advice given above, you could also look at:
I recommend that you read this post
[B4X] Features that Erel recommends to avoid to quickly polish up your old source.
I have downloaded Android version 12.
Be aware that the current version is not Android 12, but already Android 13.
How do I determine the API level of my published apps
If you still have the old source, you can find the API levels in the manifest file. This question is not relevant, because if you have installed the latest version of the IDE in accordance with the above, you can find a new dummy program (because how old is not for a long time) and add the old and the new required permissions to it to fix the permissions faults. However, keep in mind that if you take the permission too wide, you run the risk that Google will ask all kinds of security and privacy questions that you will then have to answer in that case.
If you follow the advice given here in this and previous posts, you will go a long way. For specific questions you can use the search function in the forum and where you don't come up with, you can ask a new specific question. Please indicate specifically where and how you encounter a challenge, because based on the information you provide with this question, we can only give you some generalities.
Finally, good luck with your migration process.