i have two f5 big ip virtual edition (Best bundle 200MV16) and it's service contract license expired few days age.
i want to know if i buy for example "F5-SVC-BIG-STD-L3" do i get any license key for that?
and if yes? how should i activating it? as an addon key in the reactivation process?
I am not sure what you mean by "service contract license".
For a F5 BigIP op work, you need 2 things in place
1) A valid Reg Key which you use to activate licence on BigIP.
2) Active Support Contract.
You said you have 2 VS with Best bundle. Therefore you have a valid Reg Key for BigIP modules.
So, if you are looking to activate Licence on those VS using Reg Key or reactivate Expired Licence on BigIP(previously active), you must have a Active Support contract. If you dont have a Active Support contract for those VMs, then you much get it before you can activate and use those VMs.
Following solution article explains it quite well.
If you still have questions, call F5 Support and they will verify current status of support contract, licence and explain all the options you have to move forward.
Hope it helps,