Thanks.
Your question is kind of like an oxymoron (thats not an insult if you don't understand it then go for google).
So let me clarify. If you want to find sites that physically are both tumblr and wordpress thats not really possible because tumblr is a CMS and wordpress is also a CMS, so they are both a platform to host a site.
Now if you just want to do 1 scraping run and find both wordpress and tumblr urls in the same scraping run, but realize that they are obviously 2 separate sites, then sure you can do that.
Just realize that the keywords box is like the search bar at google.com I rarely use the footprints box in scrapebox and all it does is combine whatever you put there with the keywords, but you can put it straight in the keywords box.
So where is what I think you want to do.
lets say you have 3 keywords
car
truck
boat
and you want to find both tumblr urls and wordpress urls for those keywords in the same scraping run.
put your 3 keywords in the keywords box.
then create a text file, like in notepad or similar and do like
"powered by wordpress" %kw%
site:tumblr.com %kw%
Then save that. go into scrapebox and click the M button in the upper left quadrant. Then select that text file.
You will wind up with like
"powered by wordpress" car
"powered by wordpress" truck
"powered by wordpress" boat
site:tumblr.com car
site:tumblr.com truck
site:tumblr.com boat
scrape and you will wind up with both tumblr and wordpress results in your scrape.