I don’t think every bible story necessarily had to literally happen in the way you’re probably thinking … i.e. there are visions, parables, allegories and such that I don’t think are pushed as literal accounts. E.g. I’m personally fine if Ezekiel’s army of bones or Jonah fleeing God, or the book of Job could all be kinds of narrative other than historical - not to mention Jesus’ parables (not all of which are prefaced with ‘now this is “only” a parable’).
But yes, I do believe there can be and were miracles in the literal sense too - Jesus’ healings and resurrection. Some of them might be miraculous in ways that might surprise us today if we could go back and actually look. So I’m not necessarily convinced that our usual “flannel-graph” take on miracles as magic shows is always necessarily accurate. But what convinces me that miracles did take place (both in old and new testament events) is the legacy of changed lives and resulting testimonies from the people who were affected / healed / saved etc. Whatever happened, and whatever that might look like to us if we could time travel back to actually just spectate, it had a profound enough effect on the people of the day that their oral and eventually written testimonies saw fit to record it as unmistakably God’s hand that was involved.
So to summarize - what convinces me a miracle took place is the evidence and testimonies of changed lives.
[And I’ll hastily add that this is not some robust, ‘miracle-detector’ test - which I’ve little interest in devising. Skeptics will point out that all sorts of ordinary things can change people’s lives, and they’re right. The whole “let’s get a scientific handle on miracles so we can persuade skeptics” is not a big interest of mine - and I’m skeptical of that enterprise anyway. So my definition of ‘miracle’ may be a bit different than yours. If I, seemingly by coincidence, meet somebody in an unexpected place and needed words of encouragement are exchanged or some other need is met, I’m fine calling that a miracle even though skeptics can rightly write it off as coincidence. I have no need to cajole them to think otherwise on my own terms. The Holy Spirit will blow in their lives in the season where they are ready to receive it as such.]