Hi,
If you open a browser window and log directly into your OneDrive there should be a folder called apps/joplin
On your phone when you choose to export all notes as JEX the intention is for it to be imported by Joplin on a computer. Unfortunately, as you mentioned above your computer can't run the desktop version of Joplin.
Is there any way that you can get temporary access to a computer that is capable of running Joplin?
What is your version of Windows? And how much memory do you have RAM memory?
One option you have is to download a Linux distro ISO file that can be run in live mode which means that it doesn't get installed on your computer but you boot from a USB flash drive into Linux which will run on older Hardware. You can use Rufus to create a bootable USB drive of say Linux Mint. I would get and run the Xfce Edition.
Xfce is a lightweight desktop environment. It doesn’t support as many features as Cinnamon but it’s lighter on resource usage.
This is where you can get Joplin for Linux:
Then, you install Joplin for Linux. Above.
You can mount your onedrive cloud drive in linux and the Joplin for Linux will be able to files that you exported on your phone.
If you have the OneDrive software on your mobile phone you can upload the exported data to a folder on your OneDrive temporarily. Or, you can plug your phone into your computer and copy the files to your OneDrive temporary folder.
Then, you use a program called Rclone to Mount Your onedrive in Linux. It's not straightforward because it's a command line program but you can go to their forum and create a login and send me a message and I will help you mount your OneDrive in Linux and load Joplin. I am LeoW with a pink L.
I can help you install Joplin for Linux here.
Basically, you will need to install Flatpak which is easy, and then run:
sudo flatpak install flathub net.cozic.joplin_desktop
Unfortunately, you can't simply take the exported files from the mobile version and copy them directly to the synchronization folder on your Microsoft OneDrive.
You need to come up with some way to temporarily be able to install Joplin desktop somewhere so you can restore your data that you exported from the one phone that does have your files.
Linux should run well on your older Hardware in order to accomplish this one task.
UPDATE: Possibly better idea and easer.
If your phone that has no data is properly synchronizing with OneDrive and you have no files on your OneDrive folder in Apps\Joplin you can transfer or copy the exported JEX files from the phone that has them and put them on the phone that doesn't. There is an option to import from JEX which is the output format used by your other phone.