Arduino Pro mini connection problem

Hi, my Arduino pro mini is powered by two 1.5V batteries and is connected to the computer with Gnd, Rx and Tx to com port. Unfortunely, when I try blink example i get this error: avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x30. What am i doing wrong?

Get started with the getting started guide here
If you still have trouble, post pictures of your wiring, and let us know exactly what you are doing, including what options you select on the menu, and full output of error messages.

What i did:
Used two 1.5V batteries to power up a board by connecting it to raw and gnd pins. Red LED is up, so i guess this part is ok.
then i cut half a COM wire (RS232), and connect Tx, Rx and Gnd to Arduino in this confugiration: Rx to Tx, Tx to Rx, Gnd to Gnd. Then i connected this to computer.
I selected Arduino Pro Mini board, ATmega328 (3.3V and 8 MHz) and i can't change the port, there is only COM1 available.

Use an RS-232 to TTL converter, or USB-to-serial-TTL adapter, do not connect Pro Mini directly to computer Com port RS-232 high-voltage signals.

Only select the 3.3V board in the IDE if you actually have a 3.3V/8MHz board. If you have a 5V/16MHz board, select the 5V board in the IDE even if you are powering it at 3V.

But first:
Get started by powering the Arduino using a USB-to-serial-TTL adapter which matches your Arduino as detailed in the getting started guide, and make sure you can upload using that method, and then progress to fancier things such as powering by battery later.

I have 3.3V/8MHz board. Question is if i can connect Arduino to computter without adapter somehow?

No, not a Pro Mini. It requires an adapter, and specifically a 3.3 V FTDI adapter or 5V/3.3V switchable FTDI adapter.
Other Arduinos such as UNO and Nano have a built-in FTDI adapter.