Can I use a USB-3 to USB-C adaptor to connect my CanoScan 9000 Mark II scanner to my new iMac, which has only USB-C

Yes. It should be fine to use an adaptor.

You, however, may need to find drivers for it for the new macOS version.

https://canoncanada.custhelp.com/app/answers/answer_view/a_id/1040829/~/pixma%2C-maxify-and-canoscan-products-supported-in-macos-ventura-and-older

Try these drivers: https://canoncanada.custhelp.com/app/browse/a_status/published/channelRecordID/DRIVERS_AND_SOFTWARE/currentSelectedID/RN_PRODUCT_2130/pageSize/25/productCategoryAnsList/RN_PRODUCT_2130%3ARN_CATEGORY_3319%3ARN_CATEGORY_318/productRecordID/RN_PRODUCT_2130/truncate/200/type/browse

You can also try to use the scanner without any driver and see if at least the Image Capture app can see the scanner and interact with it.

click here ➡️ Scan images in Image Capture on Mac - Apple Support

Try VueScan  . I had an earlier Cancan 8600F scanner and used VueScan with it. It's a great app and better than the apps that came with the scanner. There's a demo version you can try to see if it will work with your Mac and system.

Hi, GrammaHobbit, Yes, you sure can..... you'd need one of these adapters if the cable is indeed USB-3... (see link)

https://www.amazon.ca/Adapter-CableCreation-Function-Compatible-Chromebook/dp/B012V56C8K....you'd also definitely need to update the software for your CanoScan 9000 Mark II scanner as it only works with up to Mac OS 10.9 ??? here's a 2nd link to software for that scanner.... you can pick from Catalina and up to Monterey (Mac OS 12) https://en.canon-cna.com/support/consumer_products/products/scanners/canoscan_series/canoscan_9000f_markii.html?type=drivers&language=&os=macos 10.14 (mojave)

and that should be it

have a pleasant day

John B

+1 to what Phil0124 wrote..

check out this link, which supports Ventura ( Mac OS 13) https://canoncanada.custhelp.com/app/answers/answer_view/a_id/1041308/~/scanner-driver-%26-utilities-for-mac…. Image capture or Preview might work for test scans/tryouts… looks like a really nice scanner btw..IF the Canon driver software doesn’t work ( and it should) then your only option, afaik, is VueScan from Hamrick Software… anyways, give that link a try

John B