I wouldn’t trust a random store with any irreplaceable data - and there’s likely no recourse for you when they fuck it up. Make sure everything important is backed up.
These days, Windows assigns drive letters almost randomly. Typically after a drive reconfiguration, it’ll just label the boot drive as C: and the next one as D:.
If you’re wondering where A: and B: went, those are for the floppy drives nobody has any more because drive letters are an ancient relic and need to die.