How do I renew a travel trailers registration without the slip?

My dad owns a travel trailer that has been out of commission several years. My husband and I fixed it up to use for work purposes but the tags are almost a year out of date. My dad is working in Alaska right now at an oil refinery and we need to get the tags renewed so we can pull it. How do I go about doing that if I do not have the renewal slip?|||use whatever paperwork you have,take it to DMV. tell them you need to pay it.they will send the new stuff through the mail to the registerd owner