USB Question for important files

I want to turn my Lenovo 500e chromebook into Linux for long term use and I will keep some important files on it. Thing is I will use a USB flash drive and I know they don’t last long my question is will files be stored in the built in storage or the USB flash drive

That depends. Per the below linked docs, have you run through them and checked what board you’re using?

What files are you talking about?

my board name is phaser360

I think my storage is eMMC so I guess I won’t be able to install Linux internally

I don’t think that’s how it works. I have a robo360 which can install Linux internally.

I looked at many older posts saying it is not possible from emmc storage type is this fixed?

If you wish to install Linux on a machine with low eMMC storage, I’ll use Arch Linux as an example here, though tutorials exist for any distro.
Arch Linux has this nice utility called the archinstall script that you can run from the live ISO by just typing archinstall and hitting enter. When running through the configuration of that auto installer, be sure to choose Desktop as your profile for your system to have a GUI, but for the Disk Configuration, you can select an inserted MicroSD card along with your eMMC storage and the script will automatically use the larger MicroSD card for your /home folder that programs are installed to, and boot etc will be on the eMMC.

As a distro with a better guided install, I found the following discussion from the Fedora forums, where it looks fairly easy to do there as well: How to mount /home dir on separate partition? - Fedora Discussion

And to note, if youre not familiar with linux arch is not the distro for you.

Debian or fedora are good beginner distros

I dont believe so, though a cheap $15 micro sd card works wonders, if you use linux

I agree with Ethan about beginner distros