Hello stuckeytabitha,
Going to a retail store would be the best and safest option, however in your case you must have gotten these pieces of clothing from a liquidator so I'm not sure you'll find a store you will readily help you as they may think negative of you having pieces of clothing with security tags.
You might want to try and remove it yourself, but choose the least sell-able or expensive item to try this on.
Here are 2 of the most helpful guides I also found just like you -
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All the best!