Hong Kong is about 340 times smaller than Montana.

Montana is approximately 376,979 sq km, while Hong Kong is approximately 1,108 sq km, making Hong Kong 0.29% the size of Montana. Meanwhile, the population of Montana is ~989,415 people (6.3 million more people live in Hong Kong).
Tip: This to-scale comparison of Montana vs. Hong Kong uses the Mercator projection, which distorts the size of regions near the poles.