Hey there, @mikey007.
Glad to have you here in the Community!
When creating an Estimate you want to be sure you're selecting the Customer: Job. If you are doing this, it sounds like you may have a broken Purchase Order template.
First, create a new Purchase Order template. Then convert the Estimate to a Purchase Order using the new template.
Here are the steps:
For more details on using and customizing templates check out this article: https://quickbooks.intuit.com/learn-support/en-us/customize-forms/use-and-customize-form-templates/0...
Once you have the new template created, use it when you convert your already made Estimate to a Purchase Order.
If you have any questions or concerns please know I'm only a post away. Take care!