Hi Vijay,
When you performed the client export steps SCC8 on client 500, it should generated max the follow three files
<SID>KO<No> - For cross client data
<SID>KT<No> - client specific data
<SID>KX<No> - for client specific texts
Then you login into target client 210 then perform the import steps in STMS. Then perform the post import process SCC7.
Also, please check the follow thread
Step by Step guide for client export import - Basis Corner - SCN Wiki
Regards
Adil