A Session ID is authentication information a WhatsApp bot uses to establish or restore its connection. In MANU MD the README route is a pair code: you request a code from the project pairing route, enter it inside WhatsApp, and complete the linking to obtain the session information the bot setup consumes. A pairing code and a Session ID are not the same thing: the code is typed into WhatsApp during linking, while the Session ID is the resulting authentication information.
The README has a section titled Get Session Via Pair Code. Its button does not lead to a standalone pairing website: the link behind the button opens a Replit project published by the developer, at replit.com/@manulwijethila2/Manu-MD-V6. The README gives no other pairing address in readable text.
That Replit address no longer opens, checked on the last verified date below. So the documented pairing route is currently unavailable. When the route worked, the flow was to open the pairing project from the README, follow its instructions, and in WhatsApp open Linked Devices, choose Link a Device, choose the link with phone number option, and enter the code. Do not substitute session generators from unrelated bots, which cannot be trusted with WhatsApp credentials.
Keep your Session ID and session files private. They work like a password for the linked WhatsApp session, so never post them in public, never commit them to a public repository, and never enter them on a website that is not linked from the project repository.