I'm typing up the answer and will post in a few minutes with big spoiler marks for those who want to solve it on their own. BTW, this can be done from either direction. Just use a mirror image of the moves I suggest.
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"M" stands for the green male frogs. "F" stands for the brown female frogs. Underscore _ stands for the empty rock. I italicized the frog I am going to move.
MMM_FFF
MM_MFFF
MMFM_FF
MMFMF_F
MMF_FMF
M_FMFMF
_MFMFMF
Do you want to pause here and try the rest on your own? If so, ignore the following
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But if you're still stumped, here's the rest of the solution:
FM_MFMF
FMFM_MF
FMFMFM_
FMFMF_M
FMF_FMM
F_FMFMM
FF_MFMM
FFFM_MM
FFF_MMM
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