Error in MongoDB / Mongoose?

I'm trying to start my server, but when I try to start it, it says MongoDB error, and I've been looking for a solution to this problem for some time now, and so far I have not found anything.

What complicates even more is the fact that I was not the one who created this server, and I have never used Mongoose, just MongoDB itself.

There is an error that appears in the console when I try to start the server:

{ MongoError: failed to connect to server [127.0.0.1:27017] on first connect [MongoError: connect ECONNREFUSED 127.0.0.1:27017]
at Pool.<anonymous> (C:\Projetos\Server\node_modules\mongodb-core\lib\topologies\server.js:328:35)
at emitOne (events.js:96:13)
at Pool.emit (events.js:188:7)
at Connection.<anonymous> (C:\Projetos\Server\node_modules\mongodb-core\lib\connection\pool.js:280:12)
at Connection.g (events.js:292:16)
at emitTwo (events.js:106:13)
at Connection.emit (events.js:191:7)
at Socket.<anonymous> (C:\Projetos\Server\node_modules\mongodb-core\lib\connection\connection.js:177:49)
at Socket.g (events.js:292:16)
at emitOne (events.js:96:13)
at Socket.emit (events.js:188:7)
at emitErrorNT (net.js:1277:8)
at _combinedTickCallback (internal/process/next_tick.js:80:11)
at process._tickCallback (internal/process/next_tick.js:104:9)
name: 'MongoError',
message: 'failed to connect to server [127.0.0.1:27017] on first connect 
[MongoError: connect ECONNREFUSED 127.0.0.1:27017]' }
(node:8348) UnhandledPromiseRejectionWarning: Unhandled promise rejection 
(rejection id: 1): MongoError: failed to connect to server [127.0.0.1:27017] 
on first connect [MongoError: connect ECONNREFUSED 127.0.0.1:27017]