I've been in similar positions (as the interviewee/candidate) and would suggest you just ask those kind of questions straightforwardly/directly - either as part of the discussion if it emerges 'organically', or during the "do you have any questions" part they typically have at the end.
You could ask about specific versions of the database software they use (although there may already be a clue to this in the job ad, e.g. "proficiency with SQL Server 2008/2012/2014" would suggest that this is what they are currently using or looking to use. If this was already specified then adapt the question accordingly, e.g. "I understand from the job spec that you are working with SQL Server 2008 through to 2014? ... do you have any plans to use later versions in the near future?").
You could also ask about their approach to new technology in general, for example "would we typically be working with leading-edge versions of the systems or do you tend to stick with more established versions for a long time?"
Perhaps you could ask about how much AWS/cloud/PaaS is used in the company - would you be involved in that? - and whether they envision any movement into the cloud for their "on-prem databases".
Is it a deal-breaker for you if they stick with "older" technologies, as in would you not want to take this job (if offered?) - if so, I recommend you get a very clear answer about this during the interview.
If it's a technical interview I'd expect most of these details to be able to emerge quite naturally/organically during the discussion.
Above all take your lead from the interviewer/how the interview is going as to how to direct these questions. But please do bring them up directly (if they don't come out naturally) since it's clear that this is important to you - I'd feel the same!