I own a heavily modified Ruger 10/22 with a suppressor:
Most suppressors made for .22 lr firearms (and possibly most suppressors in general) use a 1/2x28 inch thread pattern. You can either have your barrel sent to a gunsmith and threaded, or just buy one of the many aftermarket threaded barrels that are available.
A couple things to keep in mind:
10/22 barrels come in the original size, and the larger .920 inch diameter "bull barrel." The larger diameter barrel will either require a custom stock, or some modification to your factory stock in order for it to fit properly.
If you are interested in maximum suppression you will probably also be interested in shooting subsonic ammo, as it doesn't produce the louder "ballistic crack" of ammunition that breaks the sound barrier. Because the rate of rifling twist is based on the speed of the ammo, some people who only intend to ever shoot subsonic ammo get 1:9 twist rifling instead of the standard 1:16, as it is designed to better stabilize the slower moving subsonic round.
Finally, and perhaps least importantly, there is the matter of the suppressor itself. You can buy one for $200 (not counting the tax stamp) that will be made of aluminum and designed for the .22 that will work great. However, if you ever buy something like a Mini 14., or some other rifle which shoots .223, or something like a Mac-11 with a .22 conversion kit, it is highly unlikely that that suppressor will be able to handle the significantly greater pressure created by either the .223 round or full auto fire. So if you think there is a chance that you might ever need a suppressor for a .223, or for a full auto .22, then you might consider getting a more expensive suppressor rated for either of those purposes (as it will still work great when used on your Ruger 10/22).