How triggering is it to keep my freinds who used to use drugs with me ?

It is very triggering because you will constantly be pressured or tempted to use again. You can still be friends if they honor and respect your decision to stop using. But if they encourage you to use they are not a really good friend so it might be best to stay away.

If your friends worked at a perfume shop, you would smell like perfume, even though you never worked there. If your friends worked at a coal factory, you yourself would smell like coals. If you want to gauge a person's character, look at his friends.

Trying to quit is one thing.. but having it constantly around you makes it just that much harder. When trying to quit an addiction, you have to segregate yourself from anything about it. Triggers come from things that remind you of your abuse. Being around people that abuse still, will only have a negative impact on your recovery.

that's very triggering because you probably will think about that every time that you are with them.

That depends on their attitude towards drugs. Having friends that share a common history such as having faced the difficulties of quitting can help you stay strong and avoid repeating past mistakes. If their attitude towards drugs indicates they might start using again then it is best to keep them away, don't let them drag you down with them.