Blank/Zero cell need info copied from a certain cell to corresponding one

[mckeamic]

So I have a spreadsheet doing several things, but here is what I'm stuck on. In column H {min #} if it is blank (or I can have the person put a 0), I need it to copy the number that is in the corresponding cell from column J {max #}.
So say for row 7 american white pelican it is blank {min #} H7, I need it to copy the number that is inputed in to {max #} J7, so it will have min # of 30 and max # of 30.
Where/how would I put the formula?
If it has a number inputted into column H, I don't need it to do anything.
Columns C,E,G,I are blank and just using as a spacer between columns.
Let me know if that is confusing or if anyone has any suggestions.
Thanks

A	B	C	D	E	F	G	H	I	J
3	species		temp		humidity		min#		max #
4	--		--		--		--		--
5	abdim stork		37.2		58		30	-	33
6	american goldeneye		37.2		10		20	-	30
7	american white pelican		37		60			-	30
8	australian shelduck		37.2		10			-	33
9								-

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[Special-K99]

For a formula solution:

A cell can contain a value or a formula, not both.
So if you have column H with preset values then you need to have another column, lets say K.

in K3
=IF(OR(H3<>"",H3=0),J3,H3)

Then use column K instead of column H since column K will now have values that are missing on column H.

QUESTION: Row there is NEITHER a value for H nor J, so what result do you want from that?