Replacing hardwood floor blocks with tiles

I have a conservatory with a concrete floor which stupidley we had a hardwood blocks laid on top of. These keep shrinking and expanding with the sun and look a mess, and I would therefore like to replace them with floor tiles. If I take up the blocks how will I get the tar that holds them down up, and how clean do I need to have the concrete of the tar stuff that they are bonded with. I did not lay the blocks so am not exactly sure what they are put down with but remember a green tub with something in it that looked like brown tar. Any advice would be appreciated.
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