It appears from above that what you really are looking for is SATA power output connectors on wires coming from your PSU so that you can provide power to SATA devices like HDD's, SSD's, etc. We don't commonly call that a Molex connector, and that's why I was a little confused. It also appears that you already have at least a couple of HDD's connected and working. Now, look closely at the back edge of those HDD's. You will see TWO cables to each drive. There's a narrower one with a cable that runs to a mobo SATA port - that's the data cable, and it has 7 contacts in the connector. Next to it is one about twice as wide that is on wires coming from your PSU. It contains 15 contacts and provides the power to that drive. VERY likely that power output connector is one of three or four along the same wire group coming from a socket on the side of your PSU.
With your system SHUT OFF, carefully unplug the wider power cable from the back of one drive just so you can see what it looks like, then reconnect it. Now look at all the wire groups coming from your PSU and see if there are other identical connectors not already in use. Also look at other wire groups that came with your modular PSU because there may be more SATA power outputs on cables you have not used yet. If so, see if the ones you find are enough for your needs.
OF you still don't have enough, there are two solutions. One is a simple SATA power Splitter - an adapter that converts one SATA power output into two so you can connect two SATA devices to that original one output. Something like this
https://www.newegg.com/Product/Product.aspx?Item=N82E16812198015&Description=SATA power Splitter&cm_re=SATA_power_Splitter--12-198-015--Product
Or, this one converts one to four
https://www.newegg.com/Product/Product.aspx?Item=N82E16812400127&Description=SATA power Splitter&cm_re=SATA_power_Splitter--12-400-127--Product
But if you can't find any unused SATA power output connectors, this adapter will give you two of them from a female 4-pin Molex output from the PSU
https://www.newegg.com/Product/Product.aspx?Item=N82E16812119010&Description=SATA power Splitter&cm_re=SATA_power_Splitter--12-119-010--Product
On that, the white connector is the male 4-pin Molex; as you see it is quite different from a SATA power connector.
Note that the data cable and the power supply cable for each SATA device are both needed to make that device work, and are quite differnet to prevent you from mixing them up and connecting to the wrong place. Also note this. You may find a small group of four pins (or more) on the back of your SATA drive that does NOT have a cable plugged into it. Those are special-purpose pins for diagnostic testing work with the drive, and you never plug any cable into those pins.