It will have the contract number originally assigned to it when first purchased by the original owners, and the original member number for that contract.
If it's a different use year month than your current contract, then it definitely can never be changed.
Even if it is the same use year month, I don't think Disney will (or even can) change it. You can only ask.
We have both Disney original and add-on's, and one resale. The resale is a totally different member number, but then it's also a different use year month.