The reason it's not in the database is these are user defined rectangular sections. Jed is right, the dimensions are 16" x 0.75" and 9" x 1". I wouldn't call them plate though and risk confusing them with plate elements. These properties are for beam elements. You're also going to need their orientation. This is given by the beam element's Beta angle.
If this is a matter of you having the STAAD input file but not the STAAD program, you can post it and if I have the time and can post a screenshot of what it looks like.