My organization digitized around 300 tapes a few years ago but it was more for access than for a permanent preservation solution. If you just need to digitize them to have access, we got a used tape player and hooked it to a computer using AV cables, then using the free software Audacity you can control the recording from the computer while the tape plays. It’s time consuming because it has to be done in real time but a staff member set up the equipment in her work area and did other work while the tapes played through. If you do need to hire someone to do it, you should be able to find people locally who are familiar with audiocassettes since it’s not a long outdated technology. I’m isolated in Wyoming and have been able to use local people with reel to reel equipment and a shop 90 miles away in Idaho for other audio and video formats. Happy to offer more suggestions if any of these are helpful!