Good morning Norma.
Some searching about suggests this system has been around for a while. The Royal website has the ribbon at
royalsupplies com Looking a bit further, their collections of manuals doesn't include the 310PD, but the site says that if your product isn't listed, to call their help line at 888-261-4555. This is likely your best bet for finding some assistance from people who know the product.
Hoping that helps, and good luck!
D
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