How many palindromes are there? From small to large, what is the 100th? Please write the analysis process

How many palindromes are there? From small to large, what is the 100th? Please write the analysis process

In fact, just look at the top four, and the last three can be concluded
The smallest is 1000-1000001
The second is 1001-1001
The 100th is 1099-1099901