[Bob]

How convenient of them to give measurements in apples and oranges.

Not being a nuclear physicist nor having stayed at a Holiday Inn, I have to ask -- Is there a way to directly convert a concentration (mBq per cubic meter) value to a rate (nanosieverts per hour)?

[EEGator]

https://www.epa.gov/sites/production/files/2014-08/documents/conversion_factors_rn.pdf

[AdmSmith]

Is there a way to directly convert a concentration (mBq per cubic meter) value to a rate (nanosieverts per hour)?

No:

https://www.physicsforums.com/threads/becquerel-versus-sievert.767202/

[radmanptn]

Here are a couple of links you can pursue to find an answer to that.
https://www.nrc.gov/about-nrc/radiation/protects-you/hppos/qa426.html
https://academic.oup.com/rpd/article/156/1/7/1597786/External-dose-rate-conversion-factors-of
I should add a warning, if you’re not a Health Physics professional the information at the links may make you become cross-eyed. For that matter you may end up cross-eyed even if you are a Health Physics professional.