Simon, I think 10s is quite a light gauge on an acoustic and would have some influence on volume. You ciukd try 12s.
If you do keep in mind that you may well need to re setup the guitar, including truss rod adjustment to counter the increased tension on the neck and and maintain neck relief. If not familiar and experienced in working on an acoustic then you should get it done by a pro.
Also you will find more pressure required to fret notes, which may be especially noticeable playing barre chords.
Whilst you can change your strings it’s not going to make that much difference to your guitar volume in an acoustic environment.
Probably a better thing to look at is where you are sitting I.e if your in front or close to the louder sound source then you’ll struggle to hear your guitar so move around so you are physically behind or further to the side of them.
Congrats on attending a jam session with a diverse set of instruments and singing. I hope you had fun first of all.
If you couldn’t hear your guitar imagine what the ukes and mandolin experienced? Remember - the sound from your acoustic travels out and forwards so it is likely everyone in the room heard it better than you.
@DavidP suggests that gauge 10 on a dreadnought could be worth upping - yes, they are very light and will impact the overall volume. @Rossco01 mentions room positioning and that is worth considering.
Room acoustics may also play a part but are beyond your control.
And, as @jkahn mentions, strumming with 20mm isn’t going to be very loud.
Another aspect could be finding your ‘sonic space’ in the mix. If your sound is not cutting through then think about using a capo to raise your overall pitch as it may be that your sound is sitting in the mid range which other sounds (the voices / accordion) are filling so is getting lost in the mix. Write the chord charts out to suit a guitar with capo anywhere between frets 4-7 perhaps. See this topic to help with that.
These are for electric guitars and electric and acoustic guitars produce sound in very different ways.
Electric guitar strings are designed to interact with the magnetic field of the pickup coils to generate an electric signal.
Arguably, electric guitar strings should NOT have a strong acoustic sound as that will remove energy from the strings which would otherwise be going towards generating the electric signal.
For the same reason, the strings should not be transferring much energy to the guitar body. Electric guitar bodies (at least solid body guitars) are rigid to reduce sympathetic resonance, and to keep as much energy in the strings and coupled to the pickups as possible because that’s where approximately 100% of the the sound of an amplified electric guitar comes from.
Acoustic guitar strings are designed to resonate acoustically and to transfer that vibration to the guitar soundboard.
Additionally, electric guitar strings will usually have a lower gauge than acoustic strings, which will affect the setup of the guitar, and will have a much lower tension, which will have a big impact on both the setup and the ability of the strings to acoustically transfer sound to your guitar soundboard.
Do yourself a favour and get a proper set of acoustic guitar strings. That should go some way to solving your volume issues.
I guess they would have the advantage of an unwound G string (less squeaking), but outside of that I can’t think of any other upside but plenty of downsides. The smaller string gauge could cut grooves in the guitar’s nut.