What do you all think I should do?

So about 2 1/2 years ago, I worked at a gas station. I worked there for 6 months before this happened. I was working my morning shift, the store manager left for a few minutes and came back and said "your till was short the other day and today at a total of $400, you can either pay it back or if you don't, you'll most likely lose your job).. A couple days later when I got paid for the week, she instructed me to put the money in the drop envelopes (little rectangle envelopes to drop money into the safe if we had too much money in our till or when shift change happened and we counted down our drawer) and drop it in the safe without recording it, so that it would just "pop up into the system" without having EVIDENCE.. I ended up doing what she said as I was scared to be fired.. I worked there for a few more months and then quit... When I quit, I asked quite a few people questions about security footage in general. (How long do stores usually keep footage, what are the odds that they still have it, etc). Most people said that they delete it after a year. I don't know why I never tried to do anything about it. She got fired about 6-8 months after I quit for how she said it "I mixed up some numbers". If I brought it up, I don't even know if it would do anything because she is no longer there.

Any advice is GREATLY appreciated!
What do you all think I should do?
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