storage – The device is not ready warning on Samsung A50s for USB transfer of data

I want to transfer data from my mobile phone to my external USB hard disk.
The data stored in mobile is approximately 60Gb.
But during the transfer I get error the device is not ready.
the device is not ready error

However the Samsung A50s mobile phone is connected and from computer
I am able to access the folders.
accessing mobile from computer
I am not able to understand how can I transfer mobile phone content to USB hard disk in this case.