Do you mean the Mongolia country? There is one train K23 departing from Beijing Railway Station on Saturday weekly and arriving at Ulan Bator on Sunday. And K3 leaving Beijing on each Wednesday with arrival station at Moscow also stops at Ulan Bator. From Beijing to Shanghai, both bullet trains and express trains are available. Usually, soft sleepers, soft seats, hard sleepers and hard seats are equipped on the train. For the accommodation condition, you could refer to the details on the China Train Tickets Types(https://www.travelchinaguide.com/china-trains/tickets.htm) .