Have you tried putting the PRC filename in quotes? This is necessary if it contains spaces. If you type the 1st few letters and then use <tab> to complete the filename the shell will add quotes for you if they are needed. If this is the problem you should have been getting the error "PID not valid". If not, what error do you get?
Also, A Beginner's Guide to Kindle Content
has a good discussion of which retailers allow you to specify a Kindle PID for your ebooks.