This is the common problem I have seen in almost every Linux distros (especially Debian based distros. Such as Linux Mint, Ubuntu, POP OS, etc), that VirtualBox unable to find USB devices connected to the host OS, even you installed the VirtualBox Extension Pack.
Data Transfer - Suppose you want to create a backup of your Virtual Machine, or just want to transfer data from your Pen drive to Virtual Machine (Vice versa), in that case, you must have an active USB connection.
Wifi Adapters - If you want to connect your USB dongles, external Wifi adapter to your Virtual Machines, you need USB support.
Check if you already installed an extension pack or not?
Open VirtualBox ---> Click on File menu ---> Preferences (Ctrl+G) ---> Extensions tab
If you don't find any installed extension pack, go to the VirtualBox download page (https://www.virtualbox.org/wiki/Downloads) and look for Oracle VM VirtualBox Extension Pack, download and installed it. (Extension Pack must be the same version of your VirtualBox)
[If you don't know what is your's VirtualBox version, just click on Help menu ---> About VirtualBox]
I hope at this point you have installed the VirtualBox Extension Pack successfully.
Now select your Virtual Machine ---> Right-click on it and choose Settings (Ctrl+S). ---> Come to the USB tab. Check on Enable USB controller and select USB 2.0 (EHCI) Controller or USB 3.0 (xHCI) Controller, any one of them (By default USB 1.1 (OHCI). Now click on Add USB icon.
i. Open your Linux host's terminal, type
sudo su, and enter your account password.
ii. Type the following command
sudo usermod -aG vboxusers mir (In the last command, instead of
mir use your account name such as nick, peter, etc.)
iii. Finally, reboot your PC and check the USB settings again.
Thank you very much for reading :)