command three will be down in the command section but command one and two will be in the Description section on this site on my command instructions
put this command block on repeat always, active, and unconditional
command 1:scoreboard players set @e[type=Item] TNT_I 1 {Item:{id:"minecraft:tnt"},OnGround:1b}
put this command block on chain, always active, and unconditional
command 2:execute @e[score_TNT_I_min=1,score_TNT_I=1] ~ ~ ~ execute @e[r=1,score_TNT_I_min=1,score_TNT_I=1] ~ ~ ~ /summon tnt
put the command block that has command three in it on chain, always active, and unconditional