Your answer, "3,000", is not correct.
The correct answer to
When Solomon built The House of the Lord in Jeruselem, what was the size (in baths) of the molten sea?
is
2,000
as shown by
1 Kings 7:26
which is
- KJV
- And it was an hand breadth thick, and the brim thereof was wrought like the brim of a cup, with flowers of lilies: it contained two thousand baths.
- NIV
- It was a handbreadth {That is, about 3 inches (about 8 centimeters)} in thickness, and its rim was like the rim of a cup, like a lily blossom. It held two thousand baths. {That is, probably about 11,500 gallons (about 44 kiloliters); the Septuagint does not have this sentence.}