Dir: How to migrate LXC unprivileged container

I’ve setup a Debian GNU/Linux for LXC and its subuids. I created an unprivileged user account. I created and use an LXC container for that account with “dir” backend; and this deployed directories and files owned by correspondent subUIDs and subGIDs.

Now I’ve archived whole container structure (with tar) and I want to restore it into another computer, with same environment setup.
How do I deal with different subUIDs and subGIDs ranges in target, while the ported files are owned by unmatching ranges?

How can I move UIDs and GIDs in a filetree?

Supposing I have an Ext4 filesystem with a tree owned by UIDs range 100000-165535 , and I want to move it to UIDs range 200000-265535
How can I apply +100000 to every subdirectory and file in that tree?