Hi Minakshi,
As Catalog.xml is missing, so you wont be able to import the custom action in MII 12.1.
For your reference, I have attached a specimen of catalog.xml file from sample CustomAction.jar file. Basically, Catalog.xml file contains information to identify the CustomAction i.e. AsemblyName, ClassName, Type ..etc .If possible, can you please attach your JAR file.
Best Regards
Nirjar