Hello Daniel Medina,
Since you have multiple Microsoft accounts, the easiest way to identify which one was used is to sign in to Microsoft Order History with each account and look for the Robux purchase. The account where that order appears is the Microsoft account that made the purchase.
Once you find it, check whether the Robux order shows as Completed. If it does but you still cannot identify which Roblox account received the Robux, that part would need to be checked with Roblox Support, since the Xbox/Roblox account association is handled on Roblox's side.