<span id="INSERTION_MARKER">I tested my answer first.
<span id="INSERTION_MARKER"><span id="INSERTION_MARKER">The oldest, best free little image workhorse is Irfanview, downloaded from WWW.IRFANVIEW.COM. Its menu has "Extract all frames..." under "Options", which does what you want to do.
<span id="INSERTION_MARKER"><span id="INSERTION_MARKER">Be aware that you need to download and install two files: IVIEW430_SETUP.EXE and IRFANVIEW_PLUGINS_430_SETUP.EXE. "430" is the current version, but I am using version 4.25 right now. It would be wise to re-boot after installation.
Open any type of video in Irfanview and select "Extract all frames..." under the "Options". Select what and where in its dialog box and do it.<span><span> You should store them in a separate, temporary folder. Now, open each frame in that separate, temporary folder (step through them using the cyan right arrow button) and select which frame(s) to keep. Obviously, delete all others and move the keeper(s).
Irfan would appreciate me telling you that he included a "Support Irfanview" button on the website.
Gareth