I'm glad to see you're fixing your Tria, Barbie. From the label on the Tria's original battery pack, it looks to me like the two batteries combined must produce 3.2V. That means if it contains two batteries they should be 1.6V each. I would think that 3.2V battery you are ordering would work, but you would only use one of them and, thus, probably hold a charge for less time than two 1.6V ones in series as the machine apparently had originally.
Maybe there's something I missed, so straighten me out if I'm wrong here, but that looks like the situation to me.
BTW, Jade has a good idea. If I were tinkering with one of these (being the hardware geek I am) I would add a battery bypass connector so I could use an external power supply when I want.