Hi sarahtaylor93,
Thanks for your post. I'd like to extend you a warm welcome to the Community Forum. I hope you find it a valuable resource.
We’re sorry to hear about your troubles with the pricing. The items per selling unit only appear if you track stocks in the system and this could not be altered if you already made transactions for the items. If we need to change this information the only option, we have is to create a new item. Here is the help article, units of measure for additional information.
Let me know if you need further help and we’ll be happy to assist you.
Cheers,
Shella