To print one Purchase order you would add a selection criteria (where condition) to the OpenReport statement. For example, say PONO is a unique value in your table. The On Click event of the Print command would have this code. The portion of stLinkCriteria that is in quotes is the field in your table. Of course if it's a text field you would have to adjust the quotes.
Dim stFormName as string
Dim stLinkCriteria as string
stFormName = "rptPrintOne"
stLinkCriteria = "[PONO]=" & Me![PONO]
DoCmd.OpenReport stFormName, acViewPreview, , stLinkCriteria