What kind of oil and where can i find an oil filter for my 1980 suzuki gs750l motorcycle? thanks.?

just bought it and need to do this work asap, but not very knowledgable with bikes.|||Check the owners manual if you have it or some bikes have the specific weight stamped on the dipstick. Or go to the Suzuki dealer and ask buy you filter there|||many bikes dont have a filter....you can never go wrong with 10 w 30 in cool weather and 20 w 40....20 w 50 in hot weather....call suzuki dealer and ask for filter...they will know