Hi
The engine must be in good shape.
Good compresion.
Can you see the chainsaw performing how it cut wood ? If it works well , the engine can be converted.
Brand ? Displacement?
The smaller chainsaws generally start with 30 cc aprox , this is enough for a plane for sport use with 5 or 6 Kg weight.
Put more details on saw and the fine people here can help you.
Remember you can make parts , in the lathe, not complex but you must pay.
If you have no experience in mechanics , the conversion goes difficult , you must have a mechanics of chainsaw repair shop to help you, but at no cost.
With no experience you must learn to work with a carburetor, prop adapter and may be magneto ignition, if no learn , you must pay.
I tell you it to avoid frustration
Others members in the club may help.
Good luck
Jose