There were 6 barcodes on those taxes plus other images that looked fine before I ever took these updates. I haven't mailed them in yet to forestall my arrest & imprisonment, & it looks like I've got until May 17 now. Glad you got past that error message. Yep, when it won't come in well from Windows Update, taking it manually is one of the first things to try. In fact, I did have to do that at least once, myself. Good going. And, right, you have to match the one you take to the info at "right-click START, System". You want to match Windows Version, Edition, & Architecture (x64/64-bit or x86/32-bit). Good to know you get an error message otherwise, instead of the wrong one actually installing.
Good luck, & keep us informed. Good going.
Edit: It worked for me through Windows Update on March 21, but to illustrate use of the Catalog...
(1) At "right-click START, System" mine shows: EditionWin 10 Home, Version20H2, & Architecture of 64-bit.
(2) At "START, Settings, Windows Update, Learn more" which is the Windows 10 update history site, I would click the update that failed (KB5001649)...
https://support.microsoft.com/en-us/topic/march-18-2021-kb5001649-os-builds-19041-870-and-19042-870-out-of-band-ebbe0617-3a63-467a-aaaa-2a4c68a6de33
March 18, 2021—KB5001649 (OS Builds 19041.870 and 19042.870) Out-of-band
(3) Inside that URL, it says to take the SSU (KB4598481) first. Click the link to its description, then click the link to the Microsoft Update Catalog within that one to see...

Mine is near the bottom. It doesn't fully distinguish Edition but Version & Architecture are important.
(3) Then, back in the KB5001649 URL, click its own link to the Microsoft Update Catalog & see...

Again, for me, it is near bottom. You download it, run it, then may delete the raw download.