I have a huge problem with our project and I can not open it. I hope you can help me. I tested all the other solves that I found on google but nothing could help me out with that. this is my error:

mongooseError: The `uri` parameter to `openUri()` must be a string, got "undefined". Make sure the first parameter to `mongoose.connect()` or `mongoose.createConnection()` is a string.
    at NativeConnection.Connection.openUri (/Users/user/Desktop/NEu/1/project-main/node_modules/mongoose/lib/connection.js:684:11)
    at /Users/user/Desktop/NEu/1/project-main/node_modules/mongoose/lib/index.js:330:10
    at /Users/user/Desktop/NEu/1/project-main/node_modules/mongoose/lib/helpers/promiseOrCallback.js:32:5
    at new Promise (<anonymous>)
    at promiseOrCallback (/Users/user/Desktop/NEu/1/project-main/node_modules/mongoose/lib/helpers/promiseOrCallback.js:31:10)
    at Mongoose._promiseOrCallback (/Users/user/Desktop/NEu/1/project-main/node_modules/mongoose/lib/index.js:1151:10)
    at Mongoose.connect (/Users/user/Desktop/NEu/1/project-main/node_modules/mongoose/lib/index.js:329:20)
    at Object.<anonymous> (/Users/user/Desktop/NEu/1/project-main/server.js:37:10)
    at Module._compile (node:internal/modules/cjs/loader:1101:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
[nodemon] app crashed - waiting for file changes before starting...

Thank you a lot