Hi Megan,
First, I would create a new toolbox for your project. Then, right click on the toolbox, and add a New > Spatial ETL Tool. In the opened workspace, you need to set the source data (Reader), and specify the destination (Writer). The source could be the raw existing data, maybe a shapefile. And the destination would be like a blank standardized geodatabase feature class.
So, you might want to first create a blank feature class for your county parcels, with all the standardized fields.
You'll probably need to repeat this process, and create individual tools for each county. I hope this helps to point you in the right direction. If you have more questions, let me know. I'll try and help. I do similar work with roads and address point.
Good luck,
Jason