What do you mean by 'in Picasa'. Are you referring to the Picasa software on your computer or to Picasa web albums?
If it's the former then your photos aren't 'in' Picasa . They're simply in a folder on your computer, which can be accessed by
any image viewing or editing software.
If it's the latter then your images should now be in Google Photos. Have you looked there?
https://picasa.google.com/
If you want to download a full folder of photos (from Google Photos back to your computer) see 'Download all photos or videos' here:
https://support.google.com/photos/answer/7652919?co=GENIE.Platform%3DDesktop&hl=en
You might decide that Google Photos meets your requirements as a substitute for Picasa's web service anyway. If not, consider Flickr, imgur, PhotoBucket, ImageShack, ImageVenue or Fotki.
If you're brave enough to try a foreign-language site though, you might like Rajce.net. It's a Czech site, which I use myself. (I don't speak a word of Czech but I still find it easy enough to navigate).