Afaik, the plugins which come with FL Studio will only work in FL Studio. *)
You should be able to run
FL Studio itself as a VST instrument in Reaper, but others will have to tell how well that works.
*) Image Line sells some of their plugins separately as regular VSTs which should work in any compatible DAW. Are you talking about some of those?
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edit: just saw that you got them back, thanks for the update.