Searching multiple queries using CraftCMS search function
You'd have to set up an ElementCriteriaModel with parameters adapted to your entry type and the values you're getting from the query string.

I'd recommend to read the official docs on that topic

https://craftcms.com/docs/templating/elementcriteriamodel
https://craftcms.com/docs/templating/craft.entries

After that you shouldn't miss Combined searches and filters using Craft on Webstoemp's blog, a great introduction to setting up search forms and "filtering" the results with the ElementCriteriaModel.