The subs are in VobSub (image) format. Converting to srt (text) is only possible with OCR. With good old SubRip it would take some manual labour, but maybe there are better programs available.
Spoiler:
General
Unique ID : 32658323228814200851055925164147587700 (0x1891C3A6CDF54DA2198FAB86A371BA74)
Complete name : Meet Me at the Fair (1953).fr.mks
Format : Matroska
Format version : Version 4 / Version 1
File size : 2.59 MiB
Duration : 1 h 26 min
Overall bit rate : 4 170 b/s
Encoded date : UTC 2021-06-04 16:09:05
Writing application : mkvmerge v48.0.0 ('Fortress Around Your Heart') 64-bit
Writing library : libebml v1.4.0 + libmatroska v1.6.0
Text
ID : 1
ID in the original source medium : 189 (0xBD)32 (0x20)
Format : VobSub
Muxing mode : zlib
Codec ID : S_VOBSUB
Codec ID/Info : Picture based subtitle format used on DVDs
Duration : 1 h 26 min
Bit rate : 8 722 b/s
Count of elements : 1502
Stream size : 5.41 MiB
Language : French
Default : Yes
Forced : No
Original source medium : DVD-Video