I'm going to be a contrarian and say that you shouldn't waste money on a pro-level high speed card on the K-50.
The K-50 can't write very fast at all (20 MB/sec) and even the fastest Pentax K-3ii can only write ~37 MB/sec, as shown in the comparison below. Any faster card like the extreme pro or extreme plus would be wasted because the limiting factor is the camera's writing speed, not the write speed capability of the card. So even when you're maxing out your camera's burst capability, it simply can't write any faster than the numbers given above. The price difference isn't huge since all cards are pretty cheap now, but why waste money on overkill? Also the costs can add up if you buy multiple cards or larger capacities.
Pentax K-3 II SD Card Write Speed Comparison of Fastest Memory Cards for the Pentax K3 II Digital Camera - Camera Memory Speed Comparison & Performance tests for SD and CF cards
For example (all based on my own testing or tests found on the internet, speeds are usually a bit slower in camera)
The SanDisk Extreme Pro (current gen 95 MB/s read) writes as fast as 80 MB/s. Overkill, unless you want to pay more for futureproofing. I prefer to deal with whatever future tech when it arrives, but that's a personal preference.
The SanDisk Extreme (current gen 90 MB/s read) writes at 40 MB/s in 32 GB or 64 GB forms, 60 MB/s for 128 GB. These cards are already limited by the write speed of the K-3ii. I've been using this card family in my K-1
The SanDisk Ultra (current gen 80 MB/s read) writes in the 15-20 MB/s range for 32 GB/64 GB, while closer to 40 MB/s for 128 GB. This card would be close to maxing out the K-50's theoretical write speed.
The Lexar Professional 633X UHS-I (current gen 95 MB/s read) writes in the 45 MB/s range for 32 GB/64 GB, a bit faster for 128 GB. I'm currently using this card in my K-50. Not as "name brand" as SanDisk, but still works great and is quite cheap.
32 GB Prices (all from B&H)
SanDisk Extreme Pro: $22.95
SanDisk Extreme: $16.99
SanDisk Ultra: $12.95
Lexar 633X: $14.95
64 GB Prices
SanDisk Extreme Pro: $34.95
SanDisk Extreme: $28.89
SanDisk Ultra: $21.95
Lexar 633X: $24.95
A 64GB card gives me ~1700 pictures of RAW + JPEG on the K-50. I'd recommend getting one of those cards if you're planning on taking about 2000 on your trip. I do transfer shots that I really like as soon as I can to minimize the risk of data loss. If it were up to me I'd get an Extreme if I planned on a taking a lot of bursts, and if I wasn't I'd just get the Ultra.
Furthermore, I would strongly recommend you AVOID buying cards on Amazon, even from Amazon directly (and not a 3rd party seller). Instead, buy from a reputable place like B&H or Adorama. There are plenty of reviews indicating that they have a serious issue with counterfeit cards. If you get one of those, you'll see extremely slow speeds and might not get the size you ordered. 3rd party "fulfilled by Amazon" stock is mixed with Amazon's own stock, and some unscrupulous 3rd party sellers will be selling fake cards, so there's a chance you'll get one even if you order from Amazon.