What does the number 3,4,5,6,7,8,9,10,11,and 12 mean in the bible?
Most of the time in the Bible, numbers mean exactly what they mean to most of us. They are a count of something.
Sometimes they may have other meanings. For instance, when we read in Revelation 17:9 that “the seven heads are seven mountains, on which the woman sitteth,” we know that it is a count of hills, but that it means Rome. Rome has always been called the city of seven hills.
Some scholars have proposed that the numbers 3, 4, 7, and 12 represent completeness. Seven and twelve are included because they are the sum and the product of 3 and 4 respectively. Thus the so-called Trinity is the completeness of God, seven days is a complete week, and there are twelve tribes of Israel and twelve apostles. While there may be some validity to these ideas, nothing is clear from any particular scripture that numbers have meaning other than numbers. If they do, then I would think that 5, 10, 15, and 20 would be significant because those can be counted on fingers and toes.
I know of no special significance to the numbers 6, 8, and 11. I know of no significance to 9, but some might figure it an ultimately complete number because it is three times three. Of the times the number appears in the Bible, there seems to be no special significance.
Please also see my answer at What Does the Bible Say About..The Number Seven?"
Please also see my article on this subject, The Meaning of Numbers.