They could try following the steps in this guide for importing a ColdCard wallet to Sparrow.

There should be a step where they can choose the script type and they should look for "Legacy" option.

They will still need their seed phrase or private key.

Unfortunately, Sparrow can't import a .dat file (which is how Core saves wallet info). Modern Core wallets are usually descriptor-based, which means Sparrow could import the descriptor. But a n old wallet that is p2pkh won't have a descriptor.

Alternatively, they could create a new wallet in Sparrow and send the coins from the old wallet to the new one...