Moving your KeePass database to Strongbox is as easy as adding your KeePass database file to the Strongbox app. You don't need to export it from KeePass or otherwise convert it in any way.
Strongbox supports versions 1 and 2 of the KeePass format, that is, both the KDB and KDBX formats.
Please note that particular KeePass plugins may not be supported by Strongbox (we don't know of any at the moment, but in principle this is possible). If you use any algorithms outside of the standard range of AES, Salsa20, Argon2d/2i, TwoFish and ChaCha20 you may also find Strongbox is not able to open the file.
These related help articles might also be of interest:
May 16, 2023