search on newegg for "USB 3 case"
i found this by searching it
https://www.newegg.com/Product/Product.aspx?Item=N82E16811353081&cm_re=usb_3_case-_-11-353-081-_-Product
Dell systems usually have proprietary power supplys and motherboard mounting, check the mounting for the motherboard but you will have to buy a new power supply.