Hello @VinodChakravarthy - Thanks for reaching out and posting on the MS Q&A!
To answer your question in short: yes, having APIM in front of your functions is the way to go! And it looks like we have a dedicated Learn module on this particular use case:
Expose multiple Azure Function apps as a consistent API by using Azure API Management
If you have any additional requirements that aren't covered in the tutorial above, please let me know via the comments section below and I'd be happy to help!