There is no Base program in Libre Office 6
Hello,
As an educated guess, you are on a Linux OS. Usually distro versions of LO are not installed with Base (beyond me as to why). Go to your software manager & find LO Base & install from there. Other options include using a PPA (Ubuntu PPA → LibreOffice Fresh) or getting LO from TDF(The Document Foundation)
If this answers your question please tick the 
(upper left area of answer). It helps others to know there was an accepted answer.
Thank you very much…I should check my software manager first before giving up, it was there installed already. The other options suggested by you are pretty much helpful too, thanks again.