moved blog, permalinks look different, don't work

I moved from wordpress.com to my own website. I used Velvet Blues to change the hyperlinks that go from one post to another. The new ones didn’t work, giving me a message like this:

The requested URL /Word0Press/index.php was not found on this server.

A hyperlink on the old blog looks like this:

https://sixwingedseraph.wordpress.com/2011/06/11/playing-with-riemann-sums/

On the new blog the same link looks like this:

https://www.abstractmath.org/Word%20Press/?p=1902

I used Permalinks in Settings to change the last form so that it looks like the earlier one (the “Day and Name” button.) Then nothing worked; for example, if on the main page of the blog I clicked on the name of a previous blog in the recent blogs list I got a message from the server like this:

The requested URL /Word0Press/playing-with-riemann-sums/ was not found on this server.

I’ll change them all by hand if I have to, but is there a quicker way to do it?

SixWingedSeraph