thunderbolt 2 to usb adapter

I'm assuming you've just run out of USB ports and what was already stated in this thread is correct: you just need to get a USB hub and they are pretty inexpensive. Ideally you should get a slightly fancier powered usb hub that has its own power supply. Those range from $15-$40 on Amazon.

https://www.amazon.com/s?k=powered+usb+hub&ref=nb_sb_noss_2

However, to answer your direct question, you can get what is essentially a mini-dock that can plug into Thunderbolt and gives you a USB3 port, but it's the size of a large adapter as opposed to a larger proper dock:

https://www.amazon.com/Kanex-Thunderbolt-eSATA-plus-Adapter/dp/B00LOLBBQQ ($80)

There are no simple adapters, but a Thunderbolt dock will have USB ports.

if it existed and a thunderbolt dock would both be wastly more expensive then you just getting a normal usb hub https://www.amazon.com/AmazonBasics-Port-2-5A-power-adapter/dp/B00DQFGH80