The antenna is a standard SMA antenna. You can find SMA cables to extend - just make sure they are terminated male + female (some are male male / female female)

You can also purchase higher quality antennas (just search for SMA antenna, 2.4ghz)

Here's a cable example (not necessarily a suggestion) https://www.amazon.com/RP-SMA-Female-Antenna-Extension-Cable/dp/B0085X3PRE