I want to ask how can I start my email to group tulip to ask for more information about the packages tour

You can start something like

This is in reference to your advertisement that I was going through on websites or newspaper... The pacakges looked intersting but I would like to get more information about ( you can mention the specific package you are loking for or the place to travel )...

After that you can also give them a brief idea about yourself like how many members would you be , how many days you have for your vacations and so on so that it will be easier for them to find a better match for you