What I'd do is use the last version of Lemkesoft GraphicConverter for Classic MacOS, which now has a free abandonware license. https://www.lemkesoft.de/en/products/graphicconverter/downlo...

It can open PICT resources and save to TIFF/GIF/PNG etc and it has a batch mode.

edit: Interesting. I just tried the current version of GraphicConverter 11 I have installed on Ventura and it can actually still open PICTs from resource forks! Or... it tries, but the multi-page GUI is messed up so it crops the images and doesn't display them correctly. But somewhere in there it is still reading resource fork PICTs on macOS Ventura on Apple Silicon...