Unfortunately, if the exchange collapsed without warning, your funds are in a pretty complicated situation. The first thing you need to do is look for information about whether there's an insolvency or formal bankruptcy process in the courts, because that determines everything. In many cases, when a platform collapses, digital assets get frozen and users end up in a creditors' queue. It's not the same as losing money in a traditional bank with deposit insurance, because crypto still doesn't have that legal protection in most countries.
Check whether there's a bankruptcy administrator or liquidator assigned to the exchange. If there is, you'll have to register in the insolvency process as a creditor and submit proof of your funds (screenshots, emails, transactions). Some exchanges have partially recovered assets after investigations, but others disappeared completely. Also look into whether there are class action lawsuits in your country against the platform - sometimes it's more effective to join a group than to act alone.
On the legal side, consider consulting with a lawyer specializing in commercial law or insolvency. The cost depends on how much you lost and where you live, but in some places they offer free initial consultations. Unfortunately, the reality is that many people never recover anything, so while you follow the formal process, it might be realistic to start mentally preparing yourself for that possibility.