It is not inappropriate either to ask them for a reference and/or for what they’d offer you.
However, both items should be accomplished professionally (i.e not asking for a pay scale straight up, unless you are best buddies with the hiring manager) - reach back to the HR and/or the hiring manager/old contact and tell them that your contract opportunity has successfully come to an end and that you’re now searching for the next opportunity. In that process, you plan to list them as a reference or alternatively, ask them whether they’d be happy to write your a reference letter.
And then, mention that since you had a great time working there(presumably so), ask whether they have a need for someone with your skillset(and describe your enhanced skillset covering experience you’ve gained since you left them).
Any reasonable employer with a vacancy and one whom you left on good terms, will likely offer you a role. Once they make the offer you can assess and/or negotiate per your desire.