This series of Mac can’t boot from the USB port ;-{
Your options are limited! You can boot up via a bootable optical disk (CD or DVD) or a FireWire 400 external drive
You’ll need to dig around for replacement SATA I (1.5 Gb/s) drive. Most drives today are fixed speed SATA III (6.0 Gb/s) which won’t work here. Some drives offer auto sense technology like [https://s3.ap-northeast-2.amazonaws.com/global.semi.static/Samsung_SSD_870_EVO_Data_Sheet_Rev1.1.pdf|Samsung SSD 870 EVO SSD] note the interface line lists support! Make sure the drive you get spec sheet lists is like this one, if it doesn’t don’t buy it!