. . . , and then when I reach civilisation to upload to some kind of cloud service.
If by civilisation you mean somewhere where there are computers, then I recommend you get access to a computer, plug the MPW into it using a USB connection, and use one of the cloud service web sites to upload the contents of your MPW.
I sort of did the equivalent back in 2004 when travelling, although of course there were no cloud services, no large portable hard drives, and no way to connect to my computer back home. Which was turned off anyway, and couldn’t store all the photos I had taken on its little hard drives. But there were a lot of Internet Cafes back then, and every small town had one. Some where pretty dodgy though!
Of course you are not going to be able to back up an MPW over a dial up internet connection. Even a good connection is going to take some time. An alternative would be to find somewhere where you could back up the MPW to DVD or Blu-ray discs, depending on how much data you are generating, and post them back to a safe place.
Posting important stuff back to a safe address and/or person who can store the stuff for you is always a good idea when travelling a long time abroad. If travelling remotely, it is also a good idea to make two copies of digital media on optical discs and mail one copy from each of two completely separate locations. i.e. Two towns a few days or a week apart. Stuff does get lost, or delayed for a long time, from some remote locations.
Also, if you are travelling abroad and your country has Consulates in the countries you are travelling, they will sometimes accept mail to be posted back to your safe address. This is far more secure and reliable, if they provide that service. Always check before you travel.
Enjoy the trip! Take lots of great photos!