Changing Search Type to fulltext - no option

[sempire]

I am trying to achieve the 3 letter word search - I am starting a stock market forum so 3 letter searching kis quite important. Now I understand that you need to firstly activate fulltext searching via the Mysql database rather than the native VB DB. Unfortunately in my settings, under the Search Type, the only option is DB Search and nothing else.
I am running 4.0.8.

I tried just changing the minimum search to 3 letters for the VB DB search and then reindexed the search index, but nothing worked. It still won't let me search 3 letters.

Any ideas?