Hi everyone. I’m really new to Macs so please forgive my naivety. I recently bought a 2017 MacBook Air i5 (as I was getting fed up with windows), which came running High Sierra. I wanted it to run Monterey so I downloaded the update but got the message that the drive wasn’t formatted APFS. So…I watched a YouTube video on how to do it (big mistake) and now when I switch on I get a file image with a question mark which flashes. So I guess I need to mount the drive but just can’t figure out how. Again forgive my stupidity