Hey dustee. Sounds lovely! There are several "silver" products in the store you can buy - but honestly, a trip to Sally Beauty (hair color store chain) would benefit you greatly. Or see a professional colorist. Just because I'm thinking your natural remaining brown color must be lifted 100%, first, so the new color takes properly, and is "true". You must choose just the right tone of silver or you could end up with very muddy, flat gray or purple ( ! ) hair. Try Sally, first, if you have these stores in your area. They can help you choose the ideal process.
I'll advise you to use White and silver toners, which work by canceling out the color of your hair, to give you a more neutral hair appearance. You can still use the Silver or platinum blonde, which turns your hair into a perfect silver color.