Free Credit Report Experian. I have 3 collections I do not know how to contact them

I received my free credit report from experian and have three collection accounts. They don't exceed $500, and I honestly had forgotten about them. I would like to pay them immediately, but don't know where to begin. The companies that are holding the accounts only have initials on the report and I have no way of knowing how to contact them. Can you help?
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Dispute the accounts now.
Say account not yours.
You will get a response with contact information to validate and negotiate before you pay.
or
The account will be removed deleted or cleaned from your report.