Hi, Im 19 and have no previous criminal record
Canada

I am being charged with possession of stolen property from my employer(they changed it from theft under 5000) for about $1000. Another employee was stealing and I received goods from him for being quiet. I mistakingly told the police what happened. What are the chances of me getting a criminal record?

I'm confused. Did you know the stuff was stolen and tell the cops, or did you not know and just told them that the co-workers had given you some stuff?

I knew he took them from the store

So you knew it was stolen and then confessed to the cops right? Did they ask you as part of an ongoing investigation, or was it all a coincedence? Like maybe you knew the cop and were talking about something cool you got, and he said "Hey, that's stolen".

It was an ongoing investigation.

There is about a 100 percent chance that you will have a criminal record.

1. you told the police
2. you had stolen goods ( evidence)
3. you told them all of this without working a deal out with the DA first

You should have an attorney and they need to try and work out a deal with the DA. But since you already gave them everything they need so it is not much to deal with now.