What do you do with old phone numbers you've gotten from women?

Maybe you went on a single date, or never actually met up. Or maybe you were kinda close, but it never took off. Now you're looking through your contacts list, and you have all these numbers of women you haven't spoken to in months or years.

Or maybe you always wanted to reconnect with an old date, but just told yourself "no, move on" or "it's silly" etc.

Also, what about other venues? Do you ever see that hot girl from high school online on Facebook and want to send her a cold-message?

If you do do cold contacts like this, how do you approach it?
Obviously, "be confident". Like don't call them and fumble when they answer. But, likely, they are going to be awkward about it, where you just have to push through, take control of the conversation, and act normal. Any tips for how to do this?

I specifically mean ambiguous 'endings' to the relationship. Like "haha, let's be friends" or they just never replied to a neutral text.Not like you had a break up, or they specifically said I don't want to talk to you anymore.