Paraguay is around the same size as Montana.

Montana is approximately 376,979 sq km, while Paraguay is approximately 406,752 sq km, making Paraguay 8% larger than Montana. Meanwhile, the population of Montana is ~989,415 people (6.4 million more people live in Paraguay).
Tip: This to-scale comparison of Montana vs. Paraguay uses the Mercator projection, which distorts the size of regions near the poles.