How do I use ffmpeg to convert videos (filmed VFR:120), from a playback frame rate of 120 to a PFR of 30 fps, WITHOUT RESAMPLING?

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I’ve never used ffmpeg (in Windows Command) before and am a newbie coder so any help would be much appreciated! I have videos that were filmed with a variable frame rate of 120fps. These videos have a playback frame rate of 120fps, and I need to convert them to a playback frame rate of 30fps without resampling.

I tried running the below line of code and managed to create a file that listed a frame rate of 30fps (when I left click the file I find this info within Properties >Details) , but the length of the video (listed in Properties) had not changed, I would expect the new video to be 4 times longer due to the slower playback frame rate, so I’m assuming I’m doing something wrong.. Can anybody help me alter the below code to change the playback frame rate to 30fps, while keeping frame number the same, and also not altering the length of the corresponding audio?

ffmpeg -i "C:pathVideoA001C0060_2023.mp4" -vf "fps=30" -c:a copy "C:pathVideoA001C0060_2023_convert.mp4"