Hi Dwarakanath,
Actually, AMC contract is the job of SAP partner that sold SAP B1 license to your company.
Because of that, it is not available in the sap customer portal.
The AMC contract duration is one year and its renewal must be reminder to SAP B1 end user at least 3 months before termination date of AMC.
So, I suggest to ask the SAP partner to know the AMC contract history for your company
Good luck
Rgds,
Jimmy