A quick way for large amounts of pictures, but it has several flaws:
If you have s3pe - open it.
File > open > the sims 3 folder > saves > name of save > TravelDB.package
It will open a list of files with different tags.
Type IMG, Click the checkbox, Click on Set, Check Filter active -- as shown below:

If you click on one of the lines you could see the preview, like this:

Sadly, that's going to look this way (extended/with different aspect ratio) also when saving.
In addition, the text is not captured and there is no way to know the right order of memories. These are the flaws.
Anyway if you wish to save a picture:
Right click on the line > Save Image (you can save in PNG format)
If you wish to save ALL memories of that save (=from all your sims in that save)
Then before right clicking, press CTRL+A (which selects all), then
Right click > Export > To File - then you can save wherever you want. Apparently it's not saved ia a .png format, and can be saved as .png only for individual files.
Example of how the saved image file will look like:
