I have a .flv video file from Hayley Oliver that I hope to convert to .mp4. Can anyone help me?

TIA

You should be able to convert it using VLC Media Player (it's free - and an excellent program)

https://www.videolan.org/

I believe ffmpeg will do the conversion.
There are Windows builds, but I haven't tried them.
It's command-line only, I think. Maybe someone can offer a GUI alternative.

+1 for VLC.

In all the years I've been using the excellent VLC media player, I'd never realised one could covert+save to another format.

fj, it looks like exactly what I need but how do I save, quit, and exit?

I'm presuming here that the Windows version looks very similar to the Linux version that I normally use.

I used menu Media->Convert/Save
I then uses [File]->Add to add the file I wanted to convert (in my case an m4v I had)
I then clicked [Convert/Save], then [Browse], then modified the File_Name in the lower box to have the suffix .flv instead of .m4v, then clicked [Save], then [Start].
The [x] button or menu Media->Quit quits.

For the record and why I use the command-line for so much, the same task in ffmpeg is just this:

ffmpeg -i P4080003.m4v P4080003.flv

Another program that works really well, and offers a wide selection of inputs and outputs, including reformatting, resizing etc, is HandBrake

It has lots of presets, or you can make-your-own.

And Handbrake also free

Beat me to it.

Can you send it to me via wetransfer and I will do it for you?

This is just my own opinion and not one specifically tied to PG Music, but I really like VLC for converting files as well.