376

The smallest

number in the

series is 1000, a 4-digit number.
The largest number in the series is 4000, the only 4-digit number to start with 4. The left most digit (thousands

place) of each of the 4 digit numbers other than 4000 can take one of the 3 values 1 or 2 or 3.
The next 3 digits (hundreds, tens and units place) can take any of the 5 values 0 or 1 or 2 or 3 or 4.
Hence, there are 3 5 5 5 or 375 numbers from 1000 to 3999
. Including 4000, there will be 376 such numbers.