Depends on the suffix. Looks like it should be 3 max dex with a max level req of 13 if the suffix is "dexterity".
If you get the 3-5 dex suffix of "skill" then the level req will be 34. But the 3 dex from the skill suffix doesn't apply to boots.
Arreat summit does show all of this information.
+ Dexterity
(Precision for Body Armor(60) and Boots(60) can only spawn on Magical versions of these items)
Available on
Dexterity +1-3 to Dexterity Amulets(2)[1-2], Bows(2)[1-2], Circlets(2)[1-2], Crossbows(2)[1-2], Gloves(1-12)[1](6)[1-2], Rings(1-5)[1](6)[1-2], Body Armor(13)[2-3], Boots(1-12)[1](13)[2-3]
Skill +3-5 to Dexterity Amulets(11)[3-5], Bows(11)[3-5], Circlets(11)[3-5], Crossbows(11)[3-5], Gloves(22)[3-5], Rings(22)[3-5], Body Armor(34)[4-5], Boots(34)[4-5]
Accuracy +6-9 to Dexterity Amulets(27), Bows(27), Circlets(27), Crossbows(27), Gloves(39), Rings(39), Body Armor(46), Boots(46)
Precision +10-15 to Dexterity Amulets(43), Bows(43), Circlets(43), Crossbows(43), Gloves(56), Rings(56), Body Armor(60), Boots(60)
Perfection +16-20 to Dexterity Amulets(59), Bows(59), Circlets(59), Crossbows(59), Gloves(75), Rings(75)
Nirvana +21-30 to Dexterity Amulets(72), Bows(72), Circlets(72), Crossbows(72)
https://classic.battle.net/diablo2exp/items/magic/suf.shtmlThe only information you want to see is this, I've expanded the meanings of the numbers as well:
Dexterity +1-3 to Dexterity Boots (level req 1-12)[1 dex] or (level req 13)[2-3 dex]
Skill +3-5 to Dexterity Boots (level req 34)[4-5 dex]