I cannot find the filesystem.squashfs file _asking for help

Hello Everyone, I am encountering this problem, and I need your help.

I am trying to convert an iso file to a docker image.

I am doing this on centos8 system and below are the steps that I followed.

1. yum install squashfs-tools -y

2. mkdir rootfs unquashfs

3. sudo mount -o loop HikOS-B_V2.1.0-standard-centos7.8_x86_64-20230322 rootfs

4. cd rootfs & find . -type f | grep filesystem.squashfs
but at the step, I failed to get the filesystem.squashfs, the command displayed nothing, which means I cannot get the filesystem.squashfs file, I cannot go forward.

I watched this video and here is the link on youtube.

I hope there are some friends can help me, thanks very much.

Best,
Lei