[SOLVED] move directory across devices on Ubuntu 20.04 Server

(tried posting this, my first post, before, but no luck-- hoping this one isn't a double-post now because of lag or something)

seeking help moving folder called "slop" from sdb1 (USB) to sda2 (SSD)-- lsblk below. running Ubuntu 20.04 Server on a RPi4B 8GB

"slop" contains everything necessary to download/run a MC server but I'm having no luck moving this to the SSD for improved performance

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
loop0 7:0 0 48.9M 1 loop /snap/core18/1949
loop1 7:1 0 48.9M 1 loop /snap/core18/1990
loop2 7:2 0 61.6M 1 loop /snap/lxd/19040
loop3 7:3 0 27M 1 loop /snap/snapd/11043
loop4 7:4 0 61.7M 1 loop /snap/lxd/19206
loop5 7:5 0 27M 1 loop /snap/snapd/10709
sda 8:0 0 465.8G 0 disk
sda1 8:1 0 256M 0 part /boot/firmware
sda2 8:2 0 465.5G 0 part /
sdb 8:16 1 14.9G 0 disk
sdb1 8:17 1 14.9G 0 part

/// BREAK ///
instructions to run the server are:

sudo mount /dev/sdb1 /mnt
cd /mnt
cd slop
sudo ./startserver.sh

this downloads/installs all of the server files, but it downloads/installs/runs to/from the USB

thank you in advance for your time/help