How can I make a male object from a female reference object using a mold? I have a female port (slightly larger than a USB port) from an old obsolete device. I would like to use the female port I currently have to make a mold for the male version. I have some ideas for adding the metal contacts to make it functional.

My current strategy is to use a product such as Oomoo 35 to make a silicon mold of the female port. This first mold will contain the shape of the male part I want (but will be too soft to use on its own). I will cut away any part of the mold that I don't need and use what is left to create a second mold, where I can then cast the actual male part in a hard material or resin as many times as needed.

I've never created a silicon mold before so I'm curious if that is a reasonable approach for what I'm trying to achieve. Can I use Oomoo/silicon again for the second mold or do I need to use a different material?

Is there any particular name for what I'm trying to achieve? I've been searching for strategies to this problem but I must not be using the correct query.
Your technique should work, as long as the male is a fairly close negative of the female. If that's the case, then your first mould (of the female part) will be the correct shape for the male part, and can act as what's known as a master. 

If they're not exact negatives of each other (in your case, I expect the male connector to be slightly smaller than the female port so it will fit easily, for example) then you'll need to alter this cast until it's the correct shape.

You might find it easier to cast the first mould (the male bit) in a harder material for alteration, before making another mould of the altered casting.

From then, you can follow the normal procedure and make a mould of this master so you can reproduce it.

Silicone can be used to make moulds of silicone objects, but you will need to be very careful when applying mould release agent to prevent the two pieces from bonding.