Safari Locked - Scam by "Apple Support Buddy"
My parents unfortunately were scammed recently - Safari locked on their computer with a popup saying they needed to contact Apple Support Buddy immediately to remove the virus. They were told that their "warranty had expired" and that they would need to pay $200 for them to remove the virus. They then allowed remote access to their computer for the scammer to install software - things like Ad block, etc. While in remote access, they also sent them an email and asked them to log into Apple. Very soon after the call ended, they realized afterwards this was a scam.
My question is twofold. I immediately called Apple after this, and was told I would need to backup all my files with support at the Apple store, and would then need to erase my hard drive. At the store however, Apple removed the software installed, did a scan, and said that everything was removed and that I do not need to erase my hard drive. On the support communities and elsewhere online, there is contradictory information about erasing the hard drive. So my first question is do I need to erase my hard drive? My second question is that even if I do erase the hard drive and back up my files on an external drive, can I use those files on the external hard drive on the newly erased computer? I have been told that those files could have remnants of the programs installed, however, if Apple says they removed everything, I would assume I could still use these. Any help is appreciated, am quite confused about what to do. Thank you.
iMac (21.5-inch Mid 2011)