This was shown in console on loading the mod the first time-
Modpack - https://www.curseforge.com/minecraft/modpacks/the-adventures-of-halk

[07:38:47.417] [Server thread/INFO] [at.ru.co.RuinsMod/]: Ruins mod determines World Save Dir to be at: ./world-Adventure
[07:38:47.425] [Thread-24/INFO] [STDOUT/]: [atomicstryker.ruins.common.FileHandler$LoaderThread:run:86]: Could not access the resources path for the ruins templates, file doesn't exist!
[07:38:47.426] [Thread-24/INFO] [STDERR/]: [atomicstryker.ruins.common.FileHandler$LoaderThread:run:87]: The ruins mod could not be loaded.

That log line is a bit misleading - since there are no templates included, obviously it will error for not finding any templates. But you should be able to parse structures using the ingame command, and then you will have templates. Try?

Please provide the command as I could not find any commands on the mod page or the wiki.

The first video on the mod's thread explains the ingame parser
https://www.minecraftforum.net/forums/mapping-and-modding-java-edition/minecraft-mods/1282339-1-14-3-ruins-structure-spawning-system

For server commands, see the readme in the resources folder
https://github.com/AtomicStryker/atomicstrykers-minecraft-mods/tree/1.12.2/Ruins/src/main/resources

For template specifics, look at this one https://github.com/AtomicStryker/atomicstrykers-minecraft-mods/blob/1.14.3/Ruins/src/main/resources/examplesAndDocs/template_rules.txt