Check the owners manual but typically 10W40 grade. I would strongly recommend fully synthetic over part synthetic or mineral oil, there is a huge difference in performance at temperature. Also select a major brand such as Castrol, Mobil or Shell. I work in the oil and gas industry and there is significant research out into the additives such as anti corrosion, anti foam, high temperature performance, anti-oxidation, film technology, detergent, anti-wear and many more. The engine oil has to endure harsh conditions, temperature, pressure and still protect internal components in the combustion chamber, sump, big end bearings, cams, valves even clutch (if wet clutch) and gearbox transmission. Pretty impressive really. The engine lube oil also contains some substances which deteriorate over time so it is important to change even if your bike has not done any miles. Castrol Power 1 is my choice, Ducati OEM recommend Shell. Also worth running the engine until warm then draining all oil from the sump, not sucking out from the top like dealers do. This way you ensure any particulates are drained. Then flush with either flushing oil or new oil. Ensure the filter is changed as well. Unless you have water in the existing oil, running it to get the engine warm will help drain it properly. If the bike has not ran in years can you put it on a paddock stand and put the bike into 6th gear and bar over the engine by hand by turning the rear wheel? This way you will not cause any catastrophic damage and will get the internals moving.
Motorcycle engines are highly tuned, higher revving and have tighter tolerances than car engines, all the more worth doing quality regular oil changes. Hope this helps.