Try to Keep Source Formats property is active by default in your excel template (i.e it will show same your qlikview format)
or if you unchecked that option then u have to use custom formate like below (update your field instead of Amount)
money format :
% in your measure
for more check
Thank you for your response, By the way, I am exporting to Powerpoint and not to the Excel. I want to export transparent Pivot table to Powerpoint. If you keep the Source format as checked, I am getting pivot table with white background. Which is not a requirement. and changing the data format is not working as you mentioned.