Enter the keywords 'solar panel 5v usb output' into Google and you will find what you are looking for :-)
Apart from that, I can only agree with the two previous answers: instead of an adapter, it makes more sense to buy a power station with an 8mm input.
Reason: solar panels emit between 18 -24 volts (at maximum solar radiation), which requires a voltage adjustment for USB.
At the last minute I only found an adapter with 'MC4' plugs -->
https://solarpowersupply.de/zubehor...You would have to buy another adapter '8mm to MC4', e.g. this -->
Wattstunde AK-MC-7909 adapter cable (solar cable)