Personally I’d not bother with such a solar panel. If its claiming 10W probably that means 5W which is 1 Amp and so take days of sun to recharge 10000.
I’d also really doubt the 10000 PD would even register, work, function, to be recharged from that solar panel, as 5V 1A input probably is too little. It would take perfect conditions to possibly work. Safest is to assume they won’t together unless someone has confirmed it will recharge off 5V 1A 5W.
I recommend either a bigger solar panel, something in the 20W region (which is 10W realistically, 5V 2A) or just not bother and carry a bigger Powercore with you instead and make use of wall sockets every few days. If you do go that bigger Powercore route I’d suggest buy two 10000 PD and recharge the most empty one when you get near a wall socket, or get a dual output Powerport and charge both 10000 in parallel, or investigate a bigger Powercore, with an eye on how fast you can ingest energy.
The cable isn’t the problem a Type A to C would topologically work, I’d go with something in the 2ft to 3ft region, long enough to have the Powercore in shade not in the sun but no longer as cable efficiency drops with length.
If you’re absolutely sure you want to go with solar, for long off-grid and not use the infrequent wall-socket method, then I’d suggest the simpler Powercore 10000, the non-PD version, as that’s what I have used as its simpler electronics, not PD, is more likely to work with solar. That’s my off-grid setup, I have a 20W solar panel and the Powercore 10000 (not PD) and it worked. I did conclude is not worthwhile, a better setup would be something like the 10000 PD quantity 2 and a dual port PD charger .