Trying to format an old Time Machine back up

Hi,

I am trying to format an old external hard drive that i used to use for time machine back ups. It stopped working a while ago and i've just ignored it and left it to collect dust. I now want to use it as a removable storage hard drive. However, it doesn't show in finder nor is it available to select in time machine. After looking at a few other threads they've requested i find the following info on terminal. Please can somebody help me with a solution. When i attempt to do anything in Disk Utility it just gives me error after error. I run a iMac (20-inch, Early 2008) / 2.66 GHz Intel Core 2 Duo / 4 GB 800 MHz DDR2 SDRAM / ATI Radeon HD 2600 Pro 256 MB. OS X Yosemite 10.10.5. TheExternal drive is a 1TB iomega LPHD-UP3

Jaks-iMac:~ jak$ diskutil info disk1

Device Identifier: disk1

Device Node: /dev/disk1

Part of Whole: disk1

Device / Media Name: OEM Ext Hard Disk Media

Volume Name: Not applicable (no file system)

Mounted: Not applicable (no file system)

File System: None

Content (IOContent): GUID_partition_scheme

OS Can Be Installed: No

Media Type: Generic

Protocol: USB

SMART Status: Not Supported

Total Size: 999.5 GB (999470882816 Bytes) (exactly 1952091568 512-Byte-Units)

Volume Free Space: Not applicable (no file system)

Device Block Size: 4096 Bytes

Read-Only Media: No

Read-Only Volume: Not applicable (no file system)

Ejectable: Yes

Whole: Yes

Internal: No

OS 9 Drivers: No

Low Level Format: Not supported

Jaks-iMac:~ jak$ sudo gpt show disk1

Password:

start size index contents

0 1 PMBR

1 1 Pri GPT header

2 4 Pri GPT table

6 51200

51206 243927467 1 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

243978673 32768

244011441 4 Sec GPT table

244011445 1 Sec GPT header

Thanks in advance!