So, from the looks of it, that big door in the scan of the ship extends to the roof of the room (granted, it is a bit blurry, but that is what it looks like), making it 3 meters tall. However, upon closer inspection, in that bottom panel, we see the crew walking up to it, and they are dwarfed by it immensely. Since it is top-down, we'll have to scale to shoulder width.

Average Male Shoulder Width: 18.25 inches (46.355 cm)

Width of Shoulders = 2 Pixels = 46.355 cm

1 Pixel = 23.178 cm

Length of Ship = 320 Pixels = 7416.96 cm

This ship is wholly consumed in a fiery explosion. Due to the fact that we don't have anything to scale to in the explosion image itself, we can pretty easily assume a baseline- that the explosion encompassed the ship itself, making its radius the radius of the ship.

7416.96 / 2 = 3708.08 cm

R = Y^1/3 x 0.28

R = Radius in kilometers

Y = Yield in kilotons

Doing this nets us 0.00227769679 Kilotons of TNT, or just about 2.28 Tons of TNT, Building level+. That said, this attack also destroyed the ship, which I would assume is made of some sort of advanced metal (I'd say fragmentation, but we'll add v. frag for safety).

Length of Ship: 320 Pixels (7416.960 cm)

Width of Ship: 164 Pixels (3801.192 cm)

For height, we'll scale the length of the ship to the height.

In the top frame, ship is 660 Pixels long.

1 Pixel = 11.238 cm

Height = 208 Pixels = 2337.504 cm

Volume of Rectangular Prism = 6.590e10 cm^3

Subtract 80% for this being a building to get a volume of actual steel as 1.318e10 cm^3. This is sadly disregarding volume of wings and the like, which would make this value higher for obvious reasons.

Low-End: 208 j/cc x volume = E = 2.741e12 Joules, Multi-City Block level+

High-End: 568.5 j/cc x volume = E = 7.493e12 Joules, Small Town level

I'm inclined to go with the Low-End of the destruction calc.

Tallies
Predator Creates an Explosion: 2.28 Tons of TNT, Building level+

Predator Destroys a Floating Metal Box (Low-End): 655.12 Tons of TNT, Multi-City Block level+

Predator Destroys a Floating Metal Box (High-End): 1.79 Kilotons of TNT, Small Town level