How do I fix my trailer wiring on my blazer?

[cat_man]

I have a popup tent trailer that was given to me last year by my in-laws, which is old but in good shape. I know the brake lights wiring on it works fine, because it works when hooked up to their vehicle. However, it doesn't seem to work when plugged into my Chevy S10 blazer's wiring. So, I am confident the problem lies in the wiring portion on my blazer.

So, how do I go about troubleshooting the wiring to find where the problem is? Or do I need a professional to look at this, and if so, any recommendations?

Thanks,

Kevin
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