Look at the chart above. Helm put up 82% in 5v5 defense while playing with awful teammates (17% QoT/quality of teammates) against solid middle 6 opposition (46% QoC/quality of competition). That's shown even more clearly in the chart below, where you can see that he mostly played with Detroit's lower end forwards against better competition.
In Colorado he'll get to play in a lesser role in the lineup and likely with much better teammates - particularly the Dmen behind him should be a massive step up, which should put him in a good position to succeed.
He's clearly very good at the defensive side of the game and that's why he's been brought in. As shown below his denials, recoveries, and PK are all really good - particularly when you consider that he had a 74% role difficulty (which again reiterates what is shown in the graphics above).
The possession heat maps below further illustrate the sort of player he is (these are from 2019/20).
His offense isn't great, though still on the same level as the rest of the Detroit team (-17% vs -15%). He's not helping them score much but he's also not dragging the team down.
His defense is awesome. He posted a -8% xGA/60 (which is really solid) when the rest of the Detroit team posted a +13% which is bad. So he's 21% better defensively than the rest of the Detroit team - despite often playing a bigger role than he ideally should as shown above.
On the PK its a similar story. He posted a +8% xGA/60 on the PK, which isn't great in isolation, but when you compare it to Detroit
without Helm on the PK they are at +25% which is teeeerrrible. Helm may have posted a +8%, but that outperformed the rest of his team by 17% which is pretty good.
All in all I'm happy with this signing. It fills a needed role, and based on the stats above Helm should be able to have a good impact on the ice in a more defined role on a much stronger team in Colorado.