How do i factory reset or access to my sandisk with my cell phone

First, I apologize for my bad english.
I just received my external hard drive (SanDisk Extreme Portable SSD 2TB). Plugged into my Samsung S20 Ultra, I was able to upload pictures from the phone to the external hard drive. After that, I plugged it into my Windows 10 computer to set the security password. It fragmented the external hard drive into two partitions. First : a visible partition, in which there are an executable which allows to enter a password and to open the second partition. This second partition must contain the data to be securided.
The problem is : since the security password, my Samsung S20 Ultra can no longer view the hard drive. I wanted to know how to detect the first partition on my phone, in order to unlock the second partition.
Or how cancel this security password and back to only one partition. I tried to format the disk, but only the second partition is formated. How to do a factory reset? The most important thing for me is that I can access the disk from my cell phone.
Thank you for your help.