Two relatively simple rebuttals to your premise:

(1) One can easily create a number with a non-terminating decimal expansion which makes use of a finite quantity of the digit "5". Therefore it is conceivable that one could also exist in an infinite universe which makes use of only a finite quantity of atomic structures identical to "you".

Similarly, and working in the opposite direction (complex-to-simple as opposed to the former simple-to-complex extrapolation), it is strongly believed that we exist in a universe with fixed universal constants, whose values are just-so, such that no universe similar to ours could be produced with any variation on those constants. If we may accept that as an argument that no such "universe" exists that we can perceive, then it should be just as easy to accept that no such arrangement of particles exists in our current perceivable universe which is similar in form and history to "you".

(2) Even if there exists an infinite number of yous in this universe comprising the entire scope of conceivable future selves (or, more succinctly, if the Mathematical Universe Hypothesis is correct), this argument still does not answer the question: "How do you know that we exist in that 1% of the galaxies where you're correct about surviving the operation?"