Be in the topic you want to search. (Modeling Armor in the Ukraine Crisis)
Click the magnifying glass icon in the upper right corner of the window.
Type in “BMPT Terminatior”
Select, “Search in this topic.”
A list of all posts in the topic with your search term will appear. Follow the links as desired until you find the specific post you seek.
The method suggested by 18Bravo will work even more quickly in small topics. For large and very large topics, the browser will not load the entire topic so the method I outline above is better for those.