I think what you have should work, but the data that’s available for the Amnbest part is - shall we say - novel, and requires a bit of unpicking.
First,
Yes, that’s correct.
Second, the Amnbest adapter. It mentions it is half-duplex. That’s OK, you are only sending from the emonTx RS232 to the RS485, so it also means that you can permanently enable data in that direction and never enable data in the opposite direction. (Half-duplex means you can send data in both directions, but not at the same time, hence the need to enable either the receiver or the driver.)
Further down the page, you get the pin connections.
The first catch is the emonTx is NOT labelled conventionally: Tx receives data and is looking for the other Tx pin, and Rx sends data and is looking for the other Rx pin. Confusing? Absolutely.
As the Tx only ever transmits (unless you’re programming it or calibrating it, which you will need to do with the programmer connected directly instead of the RS485 adapter), you can permanently enable the driver and never enable the receiver.
A & B. These are the RS485 connections. You may or may not need the GND connection to the other end - there was a long discussion about that a few months ago - the link is lower down.
RO – Receiver Output. You don’t need to connect this - no data will be coming in. In fact, if it does, it might well corrupt the calibration of the emonTx.
RE – Receiver Output Enable. This should be pulled high to disable the receiver. According to the diagram it does have an internal pull-up, so this can be left with no connection.
DE – Driver Output Enable (high to enable) This should be pulled high to enable the receiver. According to the diagram it does have an internal pull-up, so this can also be left with no connection.
DI – Driver Input (to Tx pin of micro controller) As I wrote above, this goes to the Rx pin of the FTDI connector on the emonTx.
GND Connect to the emonTx GND (either on the FTDI or the screw connector)
VCC. Connect to the 5 V pin of the screw connector, and you’ll need the 5 V USB power to supply the emonTx - the a.c. adapter does not supply the 5 V rail, only the 3.3 V.
And I think that should work hardware-wise. I’d advise reading https://electrical-engineering-portal.com/correct-cabling-modbus-rs485 and this topic too RS485 and other sensor cabling
Despite what the first reference says about A & B legs, if it doesn’t work it’s worth swapping them and checking, because some manufacturers apparently label them wrongly.
According to Glyn’s much earlier post, you’ll need to send the data in the EmonHubTx3eInterfacer output format in your emonTx. Depending on the age of your emonTx, it might be called that or “Key:value” format.