I want to install linux. I can't find my bootable usb when i press f2.
Ensure you make installation media with Dell Backup and Recovery in advance in case you want to revert to Windows:
Alternatively download an installation .iso (of the correct Edition):
To boot with Linux your Bootable USB needs FAT32 formatted. Use Rufus to make a Linux Bootable USB using the GPT partition scheme for UEFI computer ensuring its Fat32 formatted:
Windows FAQs and OEM Downloads