I'm trying to play with EmbersRekindled and RFTools (Because i need storage system). but i just find out that RFTools can't use Embers energy. Is there way to convert Embers into FE?

Currently there isn't, I might add something for this in the future but I have no clear plans at the moment

there's https://github.com/p455w0rd/Embersified/ mod that probably do it, but for now it abandoned.

Here are Initial Support for powering Forge Energy Machines with Ember. #16